Lot of good information in the posts above. Lots of different methods of cleaning a barrel that end up with the same results; a barrel cleaned to the satisfaction of the owner.

I have cleaned a lot of barrels over the last 40 years and have used a number of different approaches. I am satisfied that I have a clean barrel when I can soak a barrel with Hoppes Bench Rest, a mild copper remover, over night and not see any copper coloration the next day on a clean patch.

For a heavy powder fouled barrel, I usually start by removing as much of the powder fouling as possible before I worry to much about the copper. I use a good powder solvent, soak and brush (bronze at this time) and repeat until patches look pretty clean. Sometimes it looks like the barrel has blown its nose. Still have the copper to deal with. I have also used Kroil Oil as the solvent in some cases when I feel there may be a lot of copper to deal with. I have heard that the Kroil Oil may penetrate below the copper and help to break it free in microscopic pieces rather than having to dissolve it out later. Can't say this is true but it can't hurt to try.

Once I have a clean patch, powder wise, I work on the copper. I have done it a number of ways. Sometimes I pour a little ammonia cleaning solution in a cup and add a couple of drops of liquid detergent to break the surface tension in the barrel. Place the end of the barrel in the cup and use a patch on a rod to scrub the barrel. With each upstroke, solution is pulled up into the barrel. The color of the ammonia solution will quickly turn blue if copper is present. Ten to 15 minutes will really start the removal process. The longer the better. Dry, brush scrub, clean with alcohol or solvent to remove the water. Do an overnight test to see how much color appears on a patch. Repeat as necessary or do something different.

I have also used Sweets on powder clean barrels. I usually do the patch scrub and soak for 15 minutes and then run patches through to clean. Once I see that the cleaning patches have no color I am satisfied. Just take time. Not too concerned with more than 15 minutes soaking with well used barrels but would be careful to avoid doing this with a match grade barrel if I were cleaning one. It will give you a copper clean barrel with enough effort.

In some cases, I have used the Foul Out unit; especially if I can see some rust in the barrel. If you will dump the solution after the first hour, you will see the red-yellow color of the rust. Gets if out before the iron is further reduced to a form that is more difficult to remove. Unit works good for copper removal. May require removing the rod and sanding the copper off if there if more copper than can be plated on the rod during one session is present. As a final check, once you think you are through, do a solvent soak and scrub, clean and try unit again. Sometime you will find that there is still some powder residue covering the copper. Just need to ensure good electrical contact of the leads or you end up with water in the barrel for an extend period of time with not removal being performed. System works well but requires attention.

As stated before, there are a number of ways to get a clean barrel. These are the ways I have gone about getting clean barrels. I have been schooled by this Site that the best way to shoot lead and minimize leading, is do it with a copper free barrel. I have "drank the KoolAid." My cleaning does nothing to improve the physical condition of a barrel but does allow me to get the best out of what it can deliver.